Lady Nina Bracewell-Smith, who owns nearly 16 per cent of the north London club, has appointed bankers to find a buyer for her shares.

And that will put Uzbeki billionaire Alisher Usmanov and American tycoon Stan Kroenke on red alert.

Both are on the brink of mounting a bid for sole control of the Gunners.

Kroenke owns 29.9 per cent and needs just 10 more shares to take him over the amount that will trigger a formal takeover bid for the whole club.

But Usmanov’s investment company Red and White Holdings have 26 per cent and would also be in a position to take complete charge if it was able to buy Bracewell-Smith’s shares.

Usmanov and Kroenke are likely to have to shell out around £80m for the full 16 per cent, which would value Arsenal at £500m.

However, City analysts believe the fact that Bracewell-Smith has appointed the US bankers Blackstone to sell her shares suggests that she is not planning on doing a deal with Kroenke.

The pair sat on the Arsenal board together, while Usmanov is not a director.

But Kroenke was last night considering selling his shares in NFL team St Louis Rams for around £190m – cash that would fund a takeover of the Gunners.

The American, known as Silent Stan, also owns Denver Nuggets basketball team, NHL ice-hockey side Colorado Avalanche and Colorado Rapids of the Major Soccer League.

Arsenal manager Arsene Wenger is believed to be unconcerned by the possibility of Kroenke taking complete control and has previously said that he will remain happy as long as no-one interferes with his technical role at the club.

And a takeover could provide extra funds for transfers that Wenger admitted are required in the summer in the wake of his side’s humbling against Barcelona in the Champions League. After suffering a 6-3 defeat on aggregate, the Frenchman said: “We have to add something, for sure.”